Control analysis for solar panel dust mitigation using an electric curtain

An energy efficiency and control analysis is given for application of a transparent electric curtain for dust mitigation on a solar panel. The electric curtain technique has been proposed by NASA as an effective active method for dust removal from solar panels in planetary and lunar exploration, and this method also has potential for mitigation of dust build-up on terrestrial solar panels in dry environments. Since energy expenditure rate required for electric curtain operation can be significantly higher than the energy capture rate from a solar panel, a control scheme for activation and deactivation of the electric curtain is necessary to achieve optimal net energy capture. The control method examined in the current paper is one in which the electric curtain is activated when the panel output voltage decreases to a fraction V'(on) of the clean panel output voltage and deactived when the output voltage exceeds a second output voltage fraction V'(off). A combination of theoretical and computational approaches is used to determine how the energy efficiency changes with change in the threshold voltage ratios. A scaling analysis is developed that identifies a single key dimensionless parameter that influences the efficiency results. Optimal values of turn-on and turn-off voltage ratio are determined in terms of this parameter, and it is demonstrated that the efficiency decreases rapidly as the turn-off voltage ratio is raised above the optimal value. All of the efficiency predictions for a given mitigation velocity profile are collapsed onto a single curve with appropriate choice of the scaling parameters, which is then used to develop an optimal control criterion.